Researchers called for stiffer penalties for drugmakers engaged in off-label marketing after finding that Eli Lilly’s federal and state settlements did not significantly affect off-label prescribing of its antipsychotic Zyprexa.

Eli Lilly in 2009 agreed to pay $1.4 billion to settle allegations that it promoted Zyprexa for off-label uses, such as dementia and aggression. Lilly doled out an additional $290 million between 2008 and 2010 to resolve a number state investigations also concerning off-label promotion of the drug.

An analysis, conducted by researchers at Stanford University School of Medicine and Harvard Medical School and published April 7 in PLOS One, looked at anonymized insurance data about Zyprexa prescriptions among 14 million beneficiaries with commercial insurance coverage provided by UnitedHealthcare from before and after the settlement, from 2004 to 2011. They found no significant changes in prescribing trends in the three states that settled with Eli Lilly as well as in any of the states that were a part of the federal investigation.

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There were limitations to their analysis, however. The study’s authors only examined data from one commercial insurer and did not adjust its analysis for media coverage that could have affected prescribing trends — and the study only comprised one drug.

The researchers gave three possible scenarios as to why the settlements didn’t appear to have an effect on the rate of off-label prescribing, one of which is that illegal marketing practices may have persisted in spite of the settlements. The “penalties imposed on Lilly in 2009 were a fraction of the $4.7 to $5 billion in annual revenue the company earned from the drug between 2008 and 2010,” they wrote.

Second, they pointed to FDA guidance published the same year as the settlement — a document that allowed drug and device makers to distribute reprints of medical journal articles related to off-label uses — and noted that the regulation could have “created opportunities for manufacturers to promote unapproved uses.”

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Lastly, the authors suggested that the manufacturers’ earlier efforts could have already changed doctors’ prescribing habits to such an extent that the settlement may have had little effect.

The researchers concluded that while enforcement actions such as the one Eli Lilly faced over Zyprexa may keep violators accountable and generate government revenue, their findings raise doubts about the impact of federal and state investigations on off-label marketing.

“Policymakers should consider alternative ways of reducing the prevalence of non-evidence-based off-label use to complement their ongoing investigations,” the researchers concluded.